Melengestrol acetate (XI,17.alpha.-hydroxy-6-methyl-16-methylenepregna-4,6-diene-3,20-dione 17-acetate) is known to be useful as a progestation agent in the veterinary area. U.S. Pat. No. 3,359,287 (Example 4) discloses that melengestrol acetate is prepared by dehydrogenating 17.alpha.-hydroxy-6.alpha.-methyl-16-methylenepregn-4-ene-3,20-dione 17-acetate (XII) with chloranil.
U.S. Pat. No. 4,154,748 reports an alternative procedure for production of melengestrol acetate in which the last step is acetylation of 17.alpha.-hydroxy-6-methyl-16-methylene-pregna-4,6-diene-3,20-dione.
U.S. Pat. No. 3,705,181 discloses the simultaneous isomerization and 17-acylation of 17.alpha.-hydroxy-6-methylenepregn-4-ene-3,20-dione to 17.alpha.-hydroxy-6-methylpregna-4,6-diene-3,20-dione 17-acetate by reaction with acetic anhydride and p-TSA in benzene. It should be noted that the steroid of U.S. Pat. No. 3,705,181 did not contain any substitution at C.sub.16 whereas the starting material of the present invention contains the reactive methylene group at C.sub.16.